Fis is a small DNA binding protein that plays an important role in a number of cellular processes in E. coli and other enterics, including site-specific recombination systems (e.g. Hin and Gin) and transcription initiation (e.g. rRNA and some tRNA promoters). Its regulation pattern is interesting, with synthesis dramatically increasing from undetectable to 25,000-50,000 molecules/cell following upshift. The goals of this grant are (1) to understand the mechanism of regulation of fis transcription, focusing primarily on the role of initiating nucleotide concentrations (CTP), IHF, and Fis itself on the activity of the fis promoter; (2) to determine what other protein products are controlled by Fis; and (3) to understand the determinants of DNA recognition by Fis.